This combination of photos provided on April 19 by the Federal Bureau of Investigation, left, and the Boston Regional Intelligence Center, right, shows a suspect that officials have identified as Dzhokhar Tsarnaev, being sought by police in connection with Monday's Boston Marathon bombings.

The two brothers suspected of carrying out the deadly attacks on the Boston Marathon had originally planned to set off their bombs on July 4, a law enforcement official said.

The source said the suspects, Tamerlan and Dzhokhar Tsarnaev, advanced the date of their attack because they completed building bombs more quickly then they originally anticipated. The official declined to be identified and did not offer more details.

Police say the brothers detonated two bombs made with pressure-cookers in the April 15 attack on the Boston Marathon that killed three people and wounded 264.

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An attack on Boston's packed July 4 celebrations would have carried the extra symbolism of disrupting the city's widely followed Independence Day celebrations.

News of the alleged July 4 attack plan was earlier reported by The New York Times.

Tamerlan Tsarnaev, 26, was killed in a shootout with police in Watertown, Massachusetts, on April 19. His brother was wounded in the shootout and captured later that day.

The remains of Tamerlan Tsarnaev were claimed on behalf of his family on Thursday. His body had been kept at a Boston facility for more than a week.

Terrel Harris, a spokesman for the Office of the Chief Medical Examiner of Massachusetts, said a funeral services company retained by the family had claimed the body. Harris declined to provide details including the cause of death or where the body had been taken.

Dzhokhar Tsarnaev, 19, has been charged with crimes in connection with the bombing that could carry the death penalty if he is convicted, and is being held at a prison medical facility in Devens, Massachusetts.

On Tuesday, Tamerlan Tsarnaev's widow, Katherine Russell, said through an attorney that she wished his remains to be released to the Tsarnaev family.

Russell's attorney could not immediately be reached on Thursday.

Investigators have questioned Russell as they seek clues about how the ethnic Chechen brothers allegedly built the two bombs used in the attack and whether they had help.

The suspects' parents previously lived in Cambridge, Massachusetts, but have since returned to Russia. Other relatives remain in the United States, including an uncle, Ruslan Tsarni of Montgomery Village, Maryland, who has been seen in Rhode Island in recent days.

Officials said on Thursday that three men who had been charged with interfering with the investigation of the bombing were in custody at a jail in Middleton, Massachusetts, a small town about 20 miles North of Boston.

The three 19-year-olds - Azamat Tazhayakov, Dias Kadyrbayev and Robel Phillipos - had been transported to the Essex County Correctional Facility in Middleton on Wednesday after they were charged in Boston. Authorities have described them as college friends of Dzhokhar Tsarnaev.